CO_2 capture properties of alkaline earth metal oxides and hydroxides: A combined density functional theory and lattice phonon dynamics study

摘要

By combining density functional theory and lattice phonon dynamics, the thermodynamic properties of CO_2 absorption/desorption reactions with alkaline earth metal oxides MO and hydroxides M (OH) _2 (where M=Be,Mg,Ca,Sr,Ba) are analyzed. The heats of reaction and the chemical potential changes of these solids upon CO_2 capture reactions have been calculated and used to evaluate the energy costs. Relative to CaO, a widely used system in practical applications, MgO and Mg (OH) _2 systems were found to be better candidates for CO_2 sorbent applications due to their lower operating temperatures (600-700 K). In the presence of H_2 O, MgCO_3 can be regenerated into Mg (OH) _2 at low temperatures or into MgO at high temperatures. This transition temperature depends not only on the CO_2 pressure but also on the H_2 O pressure. Based on our calculated results and by comparing with available experimental data, we propose a general computational search methodology which can be used as a general scheme for screening a large number of solids for use as CO_2 sorbents.